Ball valves provide versatile valving assemblies, and are especially suited for valving fluids with fine solids intermixed therein, due to the simple opening and closing action of such valves. It is necessary to provide seats for ball valves, however, that are held tightly against the ball at all times to prevent solids entry between the seat and valve. Desirably sealing systems are provided for such valves which are resistant to corrosion even when subjected to the wide variety of chemical streams found in conventional industrial applications, they must be able to hold large pressure differences across them (such as will be imposed when the valve is in closed position), and they desirably operate over a wide range of temperatures (e.g., from cryogenic levels to about 2000.degree. F.).
According to the present invention, an assembly is provided which properly effects a seal between high pressure and low pressure areas. The assembly according to the present invention may be utilized as a ball valve which is completely solids-proof, is corrosion-resistant to a wide variety of chemical streams, can maintain large pressure differentials (e.g., 6000 psi), and can operate from cryogenic levels to high temperature regions.
The ball valve assembly according to the invention includes a valve body having a fluid conducting passageway therethrough with high and low pressure sides of the passageway, a ball valve mounted for rotation within the valve body, means defining an annular recess in the valve body adjacent the ball and in operative communication with the passageway, an annular valve seat of hard mineral, metal, or ceramic disposed in the recess, and a solid elastic material annular body disposed in the recess to bias the valve seat into tight sealing engagement with the ball. Surface means, provided on facing surfaces of the valve body defining the recess in the valve seat, are provided for defining a region between the valve body and the valve seat having a larger volume (and cross-sectional area) at the high pressure side thereof than at the low pressure side thereof with a transition therebetween. The solid elastic material body is disposed in this region and provides means for positively elastically engaging the surface means along the transition upon the application of high pressure to the high pressure side of the region. The body changes shape only microscopically. The larger volume portion of the region abruptly opens into another region having a much larger volume, and is in direct communication with the passageway.
The surface means defining the region can take a wide variety of forms. In general the surfaces are shaped so that a line of high pressure contact pressure is obtained that exceeds the fluid pressure, blocking out any fluid passage, even with pressure differentials of about 6000 psi.
One specific form the surface means can take is one or more right angle step portions formed in each of the valve body defining the recess and the valve seat. Another form comprises beveled surfaces formed in each of the valve body defining the recess and the valve seat, the beveled portions preferably having an angle of convergence of about 2.degree. to 20.degree. and including flattened parallel extensions thereof where desired. The surface means may further define two, spaced, regions with a pair of annular solid elastomeric bodies provided, one disposed in each of the regions, with an annular stop member disposed between the pair of annular solid elastomeric bodies to provide an over-travel stop that prevents excessive seat or ball motion that could overcompress the elastomeric bodies.
The solid elastic material body may be rubber, synthetic elastomers, or the like, and preferably is selected from the group consisting essentially of sponge graphite, sponge ceramic and corrosion-resistant elastomers. The solid elastic material body is preferably rectangular in cross-section, providing a very tight seal arrangement when deformed into engagement with the surface means provided on facing surfaces of the valve body defining the recess and the valve seat.
It is the primary object of the present invention to provide an improved sealing system especially adapted for a ball valve assembly. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.